Do-it-yourself replacement of a window sill on a plastic window

Recommendation points

• Dismantling of slopes
• Removing the window sill
• Foundation preparation
• Cutting the canvas
• Installation of the window sill and restoration of the foam seam
• Sealing slopes

Over time, the plastic window sill can be damaged or simply lose its attractive appearance from dirt and abrasions. We will describe the procedure for replacing it with a new one, during which damage to slopes and wall finishes will be minimal..

Dismantling of slopes

The procedure for preparing for dismantling the window sill depends on the type of slopes. They can be monolithic, that is, covered with plaster under a decorative finish, or panel – made from PVC lining or sandwich panels. Since the window sill itself is embedded under the plane of the slopes, it will be necessary to partially or completely dismantle.

With plastic slopes, everything is simple: you need to remove the corner framing profiles, and then carefully tear off the finishing panel, having previously cut the sealant seam with a sectional knife. You can recommend using a hacksaw blade to separate the plastic panel from the layer of polyurethane foam with which it is glued to the opening. The remaining foam should be removed completely, exposing the plane of the support rails to facilitate re-installation and cleaning the junction of the edge of the window sill for easy removal.

Cutting plaster slopes is more difficult, but also quite realistic. It is necessary to draw two horizontal lines along the edges of the opening with an offset of 25–30 mm upward from the window sill. According to this marking, the angle grinder with a diamond wheel is trimmed on a stone, in order to exclude damage to the frame, it must be protected with a screen, for example, with an old spatula. Typically, the depth of embedment of the window sill is 30-50 mm, that is, a grinder with a 180 mm circle will be enough. If the window sill is walled up deeper, this is not critical, it is only important that the cutting line is straight. Also, do not forget to make an undercut along the plane of the wall to the width of the ledge of the window sill behind the slope. If the walls in the room are covered with wallpaper, they are moistened with water and carefully torn off, starting from the slope angle by 20-25 cm.

Removing the window sill

With the technological method of installation, the window sill sheet has no attachment to the frame or support profile, it is fixed to the lower base of the opening by means of mounting foam. It is quite difficult to tear off the plastic by force, therefore, the window sill is often cut into fragments, which are removed one by one, which greatly facilitates the dismantling process. In most cases, division into three parts is sufficient: two outer parts, 20-30 cm wide, and the remainder in the center. If the window is wider than 100 cm, the middle section can be split in half.

For cutting, you can use a grinder with a diamond wheel, but the risk of damage to the frame by carelessness is so great. It is much better to arm yourself with an electric jigsaw with the cheapest saw for wood, the edge of which is cut to reduce the effective depth of the blade to 20 mm. Please note that this method is relevant only if there is a foam seam under the windowsill, but if the seal is made with cement mortar, you should use an angle grinder or a renovator, and finish the cut with a hand tool.

Dismantling the curtain can be complicated if the window sill is mechanically attached to the window block. In this case, remove the ebb from the outside of the window, and then unscrew several self-tapping screws from the support profile. Also, the window sill can be fastened with brackets to the wall at the bottom. In order not to damage the finish, the canvas must be cut so that fragments 10 cm wide remain in the place where the brackets are installed, which, after removing the rest of the parts, are easily released by lateral shift.

Foundation preparation

Before installing a new window sill in place, it is necessary to prepare the lower plane of the opening and clean out the grooves in the slopes. When replacing a window sill, it is recommended to re-install it in the most technologically advanced way with the formation of the bottom foam seam. This will help eliminate shortcomings in the thermal protection of the window opening and facilitate the installation process..

To begin with, you should remove the remnants of building mixtures and all kinds of linings used during the initial installation. As a result, only the body of the structural wall layer should remain. If the window sill rested directly on a monolithic surface, a furrow up to 70 mm wide and 20–30 mm deep should be selected under the frame. In parallel, it will not be superfluous to assess the state of the foam under the window frame: if it is darkened and brittle, it is better to remove it and re-form the foam seam.

The grooves in the lower part of the slope must allow the body of the window sill to sink at least 30 mm into the body of the wall. To remove excess material, use a flat chisel perforator to carefully clean the groove to the desired depth. Work should be done carefully to prevent large fragments from chipping off in the outer part. If the wall material is too brittle or deep cracks are present, it is recommended to pre-drill several weakening holes with a 10-12 mm drill.

Cutting the canvas

The canvas of the new window sill must be cut in such a way that it has the same protrusion above the plane of the wall along its entire length and at the same time protrudes beyond the slopes to the required distance. First, trimming is performed in the longitudinal direction so that the width of the web ensures that the radiator installed under the window overlaps. Please note that the window frame may not be parallel to the wall plane, in such cases the cutting line must be marked with the required offset.

Trimming the edges of the canvas should be carried out so that in the area adjacent to the frame, the window sill is recessed into the body of the wall by at least 30 mm. The protrusion of the sill behind the slope can be arbitrary, but it should not be less than the width of the framing profile of the plastic slope. For monolithic slopes, the average overhang is 50 to 70 mm. Therefore, the cross cut is almost always performed along an oblique line..

Installation of the window sill and restoration of the foam seam

The window sill is installed with a cut longitudinal edge close to the support profile. At the same time, at the docking point, it presses the upper plane against the frame, and in the middle part it rests on a set of pads, which are used as mounting wedges. The pads must be selected in advance and placed with an offset of 80–100 mm from the wall plane. The thickness of the lining should be chosen so that the window sill has a slope from the window of the order of 2-3 mm.

Before installing the window sill, it is necessary to restore the foam seam under the frame. When the foam has dried “to a touch”, the canvas is pushed into place and abutted against the support profile, and then a slight oppression is placed on the edge, making sure that the window sill is tightly pressed against the bottom end of the frame. Installation can be continued after 10-15 minutes, when the foam under the frame finally expands. First, a portion of the foam is introduced into the deepest part of the gap under the windowsill with a uniform flagellum 15–20 mm wide. The foam must be applied to the full thickness of the seam so that when expanding, it reliably presses the window sill to the frame.

After half an hour, an additional bend weighing 7-10 kg over each lining is installed on the windowsill. After that, the rest of the gap is filled with foam, but already in the amount of half to one third of the joint width, with the expectation of subsequent expansion. It is not necessary to apply foam in the front part of the gap; an indent of 20–30 mm from the wall plane is necessary for correct sealing with a cement-sand mortar. If the finish is represented by clapboard or sheet materials fitted close to the window sill, then first the foam is applied to the lower plane of the slope in excess volume, then immediately a plastic sheet rests against the support profile, which lies on the lining and is pressed with heavy pressure.

Sealing slopes

It is better to start sealing the slopes and walls under the windowsill the next day, when the foam is guaranteed to expand and harden. As in the case of dismantling, it is the least problematic to restore the panel slopes: they start behind the end of the frame, a small amount of foam is introduced into the gap between the panel and the wall, then the slope is pressed against the support rails. The joints between the slopes and the window sill with the frame can be sealed after 2-3 hours with white acrylic or latex sealant.

Sealing of monolithic slopes is carried out with cement mortar, which must be crushed with a spatula to the full depth of the groove. When the mortar has set, which can be accelerated by adding a small portion of stucco, it is necessary to level the embedment with the plane of the wall and slope with an abrasive teer. After that, puttying is performed for the final leveling and restoration of the finishing layer..